Frequency-adaptive sinusoidal signal integrator for grid-connected inverters in weak grids

Sinusoidal signal integrator has the capability of controlling the ac current with zero steady-state error. However, their performances significantly degrade in case of the frequency variations with the steady-state error. So far, no literature has addressed the quantitative analysis of this steady-state error. Therefore, this paper reveals, for the first time, a theoretical guidance to get the accurate quantitative analysis for the error evaluation. Meanwhile, a frequency-adaptive sinusoidal signal integrator is proposed aiming at eliminating this steady-state error. The proposed strategy is suitable for grid-connected inverter applications in weak grids where the grid frequency may experience fluctuations. Detailed analysis and results verify the effectiveness of the proposed strategy.